Skyhold is a a main Hub in Dragon Age: Inquisition. To access the area, you must first complete the Setback in Haven, and have advanced the main quest to From the Ashes.

You will have the option to customize Skyhold and its fortifications and decor, such as its throne, drapery, and even beds. Skyhold replaces Haven as the hub where the War Councill will meet, and will add the element of ruling over others in the quest chain Sit in Judgement. Most of the Inner Circle quests initiate in this area, and it is the main point of interaction with your party members, so talk to them often.